EasyFiles4 min read

Unix File Path Regex

Validates an absolute Unix-style file path such as /home/user/file.txt, rejecting relative paths and double slashes.

#unix-path#file-path#files#validation#filesystem

Regex Pattern

^/(?:[^/]+/?)*$

Pattern Breakdown

Hover over a token to see what it does.

^/(?:[^/]+/?)*$

Token	Meaning
^/	Anchors to the start of the string and requires the path to begin with a root slash
(?:	Opens a non-capturing group for one path segment
[^/]+	Matches one or more characters that are not a slash, i.e. a segment name
/?	Matches an optional trailing slash after the segment
)*	Repeats the segment group zero or more times to allow any path depth
$	Anchors the match to the end of the string

Detailed Explanation

What it does

This pattern validates that a string is an absolute Unix path: it must start with a forward slash and consist of zero or more segments, each containing at least one non-slash character, optionally separated by single slashes. The bare root path / is also valid on its own.

Why it works

The leading ^/ enforces an absolute path. Each repetition of the group (?:[^/]+/?)* requires at least one non-slash character before an optional slash, which means two consecutive slashes can never be consumed since there is no way to match zero characters between them, correctly rejecting paths like /home//user.

Common use cases

Validating file path input in a Linux or macOS command-line tool
Sanitizing user-supplied paths before use in filesystem operations
Detecting absolute Unix paths embedded in configuration files or logs
Distinguishing Unix-style paths from Windows paths in cross-platform code

Edge cases

The bare root path / is valid because the repeated group can match zero times
A trailing slash, as in /home/user/, is valid since the optional /? at the end of the last segment allows it
Consecutive slashes, as in /home//user, are rejected because a segment requires at least one non-slash character
Relative paths like home/user or ./config are rejected since they do not begin with a leading slash

Limitations

Does not reject the reserved null byte or verify segment length limits enforced by real filesystems
Treats any non-slash character as valid within a segment, including characters that are unusual in practice like newlines
Does not resolve or normalize . and .. segments; it only checks syntactic shape

Interactive Tester

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Open in Playground →

/home/user/file.txt / /home/user/

1 match

Test Cases

Editable — add your own inputs to see if they pass.

Input	Expected	Result
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Language Variants

Production-ready examples in 12 languages.

const unixPathRegex = /^\/(?:[^/]+\/?)*$/;
console.log(unixPathRegex.test('/home/user/file.txt')); // true

Common Mistakes

Using .* for segments, which allows slashes inside a single segment and defeats path structure validation

Fix: Use [^/]+ so each segment is explicitly bounded by slash characters

Forgetting the leading ^/, allowing relative paths to pass as valid

Fix: Anchor with ^/ so only absolute paths starting at root are accepted

Allowing zero-length segments, which lets malformed paths with double slashes validate successfully

Fix: Require [^/]+ (one or more) rather than [^/]* (zero or more) for each segment

Performance Notes

The pattern uses only bounded, non-overlapping quantifiers, so it has linear time complexity with no catastrophic backtracking risk
Because each segment requires at least one character, the engine cannot loop on empty matches within the repeated group
Anchors at both ends keep the check a full-string match rather than a scan for a substring

Browser Compatibility

Engine	Supported	Notes
Chrome	Yes	—
Firefox	Yes	—
Safari	Yes	—
Edge	Yes	—
Node.js	Yes	—

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